RDM vs. VMFS on ESX 3.5 ?

[Former Member]

Dear experts,

On of our customer is planning to migrate their development and integration systems plus a couple production application servers on VMWare ESX 3.5.

We have already read several sap notes on the subject but have not

found anything mentioning the best practice concerning RDM (equivalent of Raw Device) vs.VMFS ?

We opened a call at SAP and they mentioned the note "1056052 - Windows: VMware ESX Server 3 configuration guideline" which only talks about VMFS.

I was wandering if any one of you had had experience on this subject ?

Thank you in advance for your reply.

Best regards,

Fabrice Dréval

SAP Team, T-Systems France

[Former Member · Accepted solution]

Hello,

I've worked with a few virtualized SAP systems on VMwareESX and all of them were configured using VMFS.

It is by the way what VMware recommends. RDM is mainly used for Cluster Quorum/Data disks.

Quote from VMware paper:

VMFS is the preferred option for most enterprise applications, including

databases, ERP, CRM, VMware Consolidated Backup, Web servers, and file servers

From the same paper, it seems also that VMware established that both methods run almost with the same performances.

Have a look at this paper here : [Performance characteristics of VMFS and RDM|http://www.vmware.com/files/pdf/vmfs_rdm_perf.pdf]

Remember to be careful about disk alignment be it on ESX while creating the datastore as well on guest O/S when configuring the virtual disk drive --> [Recommendations for aligning VMFS partitions|http://www.vmware.com/pdf/esx3_partition_align.pdf]

Have fun, VMware is a nice product to play with.

Seb